WASHINGTON
— The US Supreme Court has made it easier for workers to sue their bosses for acts of retaliation in the workplace.

In a unanimous decision announced Thursday, the high court established a relatively broad standard empowering employees to take their supervisors to court if they retaliate after the worker has complained about illegal discrimination.

Such lawsuits, which hinge on the antiretaliation section of Title VII of the Civil Rights Act, have more than doubled in the past 10 years. They now account for 30 percent of the cases filed with the Equal Employment Opportunity Commission (EEOC), according to lawyers involved in the case. The average retaliation lawsuit costs about $130,000, the lawyers say.

The Civil Rights Act bars discrimination based on race, color, religion, sex, or national origin. But it also forbids employers from taking adverse action against an employee who attempts to report workplace discrimination.

The question before the high court was: How serious must the retaliation be to qualify as an unlawful employment practice under the civil rights law? Must an employee face a sanction as serious as losing one's job? Or would any adverse action by management that might prevent a worker from speaking up about discrimination qualify as illegal retaliation?

Federal appeals courts across the country have provided vastly different answers to the same questions. On Thursday, the Supreme Court set a single standard in a case called Burlington Northern v. White.

The antiretaliation provision seeks to prevent employers from interfering with their workers' ability to complain about discrimination, writes Justice Stephen Breyer for the court. "It does so by prohibiting employer actions that are likely to deter victims of discrimination from complaining to the EEOC, the courts, and their employers."

Managers and bosses displaying behavior like "petty slights, minor annoyances, and simple lack of good manners" does not constitute deterrence, writes Justice Breyer. But "the significance of any given act of retaliation will often depend upon the particular circumstances. Context matters."

The decision comes from a case filed by Sheila White, who complained about sexual harassment while working in a Tennessee rail yard as a forklift operator for the Burlington Northern & Santa Fe Railroad Company.

A company investigation supported Ms. White's claims. Her supervisor was suspended for 10 days and ordered to attend a sex-discrimination workshop.

A few weeks later, White was reassigned from her coveted forklift job to work as a track laborer. Both jobs were contained within the same job description and both earned the same level of pay and benefits. But the laborer job was physically more demanding and required working outside in all weather conditions.

In addition, after a dispute with another supervisor, White was suspended without pay for 37 days pending an investigation of alleged insubordination. She was later reinstated with full back pay.

White sued the company in federal court, claiming the reassignment and her suspension without pay were forms of illegal retaliation for her earlier sexual harassment complaint. A jury awarded her $43,250 in compensatory damages for emotional distress and related doctors' bills.

A federal appeals court panel ruled that the award should be reversed because neither of the two actions taken against White were adverse enough to qualify as illegal retaliation under Title VII. But that ruling was reversed by the full Sixth US Circuit Court of Appeals, which upheld the jury verdict for White.

In affirming the Sixth Circuit decision, the Supreme Court said the test is whether the employer's retaliatory acts are likely to dissuade a reasonable employee from complaining or assisting in complaints about discrimination.

The high court stressed that judges must consider the unique circumstances of each situation. "The real social impact of workplace behavior often depends on a constellation of surrounding circumstances, expectations, and relationships which are not fully captured by a simple recitation of the words used or the physical acts performed," Breyer writes.

He offered two examples of potential retaliation. "A schedule change in an employee's work schedule may make little difference to many workers, but may matter enormously to a young mother with school age children."

He added, "A supervisor's refusal to invite an employee to lunch is normally trivial, a nonactionable petty slight. But to retaliate by excluding an employee from a weekly training lunch that contributes to the employee's professional advancement might well deter a reasonable employee from complaining about discrimination."